1. The Field of the Invention
The present invention is in the field of clothing for use in protecting a human or animal from burning, hot and/or corrosive materials.
2. The Relevant Technology
Fire retardant clothing is widely used to protect persons who are exposed to fire, particularly suddenly occurring and fast burning conflagrations. These include persons in diverse fields, such as race car drivers, military personnel, fire fighters, and metal workers, each of which may be exposed to deadly fires, heat, and extremely dangerous incendiary conditions. For such persons, the primary line of defense against severe burns and even death is the protective clothing worn over some or all of the body.
Even though fire retardant clothing presently exists, such clothing is not always adequate to reliably offset the risk of severe burns, or even death. This is particularly true in the case where a person is not only exposed to flame or high heat but contacted with hot or dangerous substances, such as a hot molten metal, hot liquid, hot gel, hot solid, hot sparks, hot acid, or other corrosive material. For example, splashing of sparks and molten metal could occur in the case of welders and steel or other metal workers who routinely handle molten metal as it is poured and otherwise transported to manufacture finished steel and other metal products.
Flammable fabrics such as cotton, linen, wool, silk, polyester, rayon, polyamides, cellulose acetate, and regenerated cellulose have been treated with fire retardant finishes to enhance fire retardance. While this may temporarily increase the flame retardant properties of such fabrics, typical fire retardant finishes are not permanent. Exposure of the treated fabric to UV radiation (e.g., sun light) and routine laundering can greatly reduce the fire retardant properties of the fabric. The user may then have a false sense of security, thus unknowingly exposing himself to increased risk of burns. There may be no objective way to determine, short of being caught in a fiery conflagration or similarly dangerous environment, whether a treated garment still possesses sufficient fire retardance to offset the risks to which the wearer may be exposed.
Conventional fabrics have also been treated with water-proofing materials to make an all-weather product. For example, U.S. Pat. Nos. 5,004,643 and 5,418,051 to Caldwell describe a treatment process for applying a silicone polymer to a fabric to render it permanently water repellant. However, the fabrics disclosed in the Caldwell patents do not provide adequate protection to a wearer exposed to hot high heat capacity materials, such as hot molten metal, hot liquids, hot gels, hot solids, or hot sparks, or hot corrosive materials, such as hot acids.
U.S. Pat. Nos. 6,287,686 and 6,358,608 to Huang et al. disclose a range of yarns and fabrics that preferably include about 85.5-99.9% by weight oxidized polyacrylonitrile (“O-Pan”) fibers and about 0.1-14.5% by weight of one or more strengthening fibers. U.S. Pat. No. 4,865,906 to Smith, Jr. includes about 25-85% O-Pan fibers combined with at least two types of strengthening fibers. Flame retardant and heat resistant fabrics made according to the Huang et al. patents are sold under the name CARBONX by Chapman Thermal Products, Inc., located in Salt lake City, Utah. Such fabrics typically have a weight ranging from about 4-12 oz/yd2 (e.g., about 7.5-11.5 oz/yd2). A cut resistant version of the fabrics in Huang et al. is disclosed in U.S. Pat. No. 7,087,300 to Hanyon et al., which discloses adding metal, ceramic or O-Pan filaments to the O-Pan/strengthening fiber fabrics in Huang et al. Such fabrics were heavier as a result of including metallic filaments and were about 8-20 oz/yd2.
Although the fabrics in Huang et al. and Hanyon et al. do not burn or melt like conventional fabrics, they nevertheless contain mostly organic materials and are still capable of charring and shrinking when exposed to molten metal, burning flammable materials, or other hot materials for extended periods of time. This can weaken such fabrics to the point of forming a hole or tear that compromises their ability to provide continuous protection to a living being or object. For example, when exposed to hot molten iron, such fabrics may suffer irreparable damage, thus offering little protection to a person exposed to hot high heat capacity materials, such as hot molten metal, hot liquids, hot gels, hot solids, or hot sparks, or hot corrosive materials, such as hot acids.
Typically, fabrics that are not prone to charring and shrinkage are made from inorganic materials, such as asbestos or fiberglass. However, such fabrics are also very heavy, are uncomfortable to wear, and are not suitable for or used to make clothing, such as shirts, pants, jumpsuits, and the like. Instead, they are typically fashioned into heavy blankets or thick gloves that are many times heavier. Dixit, “Performance of Protective Clothing Development and Testing of Asbestos Substitutes,” Performance of Protective Clothing, ASTM STP 900, R. L. Barker and G. C. Coletts, Eds., American Society for Testing and Materials, Philadelphia, 1986, pp. 446-460 (“Dixit”) discloses the use of heavy weight fiberglass gloves as substitutes for asbestos. The fiberglass fabrics in Dixit had a weight of 32-35 oz/yd2, which was only slightly less than the 40 oz/yd2 of the asbestos comparison fabric. Dixit disparaged fabrics made from organic fibers such as aramid and carbon (heat stabilized polyacrylonitrile) because they lack the high temperature and thermal stability properties of asbestos and give off toxic gases when used in high temperature applications where asbestos is used. Dixit discloses coating fiberglass fabric with silicone but teaches that such coating should be applied to one side in order to retain the soft hand and feel of the fabric on the uncoated side. According to the Caldwell patents, applying a “coating” of silicone to a fabric creates an uncomfortable fabric that lacks flexibility and breathability. Dixit does not disclose lightweight, flexible fabrics that offer adequate protection from hot dangerous materials while still being comfortable to wear.